The present invention relates to a control apparatus for an electric variable valve actuation mechanism that adjusts valve actuation of either or both of an intake valve and an exhaust valve in an internal combustion engine.
For example, Japanese Laid-Open Patent Publication No. 2004-150397 discloses an electric variable valve actuation mechanism that adjusts the valve actuation of either or both of an intake valve and an exhaust valve in an internal combustion engine. The mechanism uses an electric motor as a drive source. Such an electric variable valve actuation mechanism normally eliminates the period during which the intake valve and the exhaust valve are both open, or valve overlap, in the engine starting process, thereby limiting backflow of exhaust gas discharged from the combustion chamber to the combustion chamber or the intake port.
In recent years, in order to improve the combustion performance during the engine starting process, a configuration has been adopted in which, instead of completely eliminating the valve overlap, the opening timing of the intake valve is slightly advanced to control the valve overlap during the engine starting process.
As shown in FIG. 6, an electric motor 22 of an electric variable valve actuation mechanism 2 as described above shares a battery 40 (power source) with a starter motor 32 of a starter 30 (starting device) and an electronic control unit 1. Reference numeral 34 represents an ignition switch. Therefore, when controlling the valve overlap during the engine starting process, electricity from the battery 40 must be supplied to an electric variable valve actuation mechanism 2 as a matter of course. However, the supply of electricity from the power source 40 to the electric variable valve actuation mechanism 2 during the engine starting process results in insufficient supply of electricity to the starter 30, which can reduce the driving force of the starter 30. That is, in this case, while advantage of an improved combustion performance is obtained by controlling the valve overlap during the engine starting process, there is a drawback in that the supply of electricity to the electric variable valve actuation mechanism 2 reduces the driving force of the starter 30, and that the starting performance of the engine is reduced. If such drawback related to the reduced starting performance outweighs the advantage of the improved combustion performance, the activation of the mechanism 2 can degrade the starting performance of the engine.